Lead-acid battery sulfation


Lead-acid batteries basic


A lead-acid battery is producing electricity by converting lead, lead oxide and sulfuric acid to lead sulfate and water. Below is this reaction presented in more formal way.


Pb+Pb02 +2H2SO4 → 2PbSO4 + 2 H2O+ electricity


When the battery is charged you add electricity and reverse the procedure in which specific gravity is increased. Each cell in the battery has a nominal voltage of 2 Volt. 6 cells add up to 12 V and that is a normal start battery.  Each cell has two plates. The negative plate is made of sponge lead (Pb) and the positive plate consists of lead oxide (PbO) and red lead (Pb3O4), lead sulfate (PbSO4) and sulfuric acid (H2SO4) mixed with proprietary binders and expanders. The picture below shows a new fully charged, sponge lead battery plate.


new bat plate1




When the battery is discharged a finely divided, amorphous form of lead sulfate is covering both the positive and the negative plates. Successively when the number of discharge and charge is growing the ability to generate electric power is decreasing due to defects that starting to occur.  The primary cause is sulfation. It occurs when the amorphous lead sulfate is converted to a very stable crystalline form. This crystalline form of lead sulfate reduces the active surface and thereby reduce the ability generate electric energy and in the end will cause battery failure. The complexity of the different processes makes it possible only to mention the mains causes for sulfation: acid stratification, excessive battery discharge, chronic undercharging, sparely uses and leaving batteries in a discharged state. Below is a picture showing a battery plate with crystalline lead sulfate. Note more dense structure and the hardened surface on the plate.




The impact of sulfation on the battery

The clear symptom of a battery being sulfated is higher temperature during charge and discharge. When internal cell resistance increases it is necessary to work with higher voltage. During discharge should the battery deliver the same power and as the voltage is lower the current needs to increase and the working temperature increase. The effective running time vehicles decreases together with acid gravity decrease as well. The charge time decrease as the battery only can assimilate less electric energy.


Sulfation affects the surrounding electrical components

Under performing batteries affects most of the electrical components in vehicles such as cars, buses and forklifts etc.  It reduces the life time of starters, contacts, motor windings and electronic components. Downgraded battery performance increase maintenance expenditures which in turn reduce the efficiency of the labor force.

 The solution to sulfation is to use The Regenerator from Cobatec. The Regenerator can be adapted to preventive service or full regenerative service as well to any desulfation service in between those two treatments.